Explosion-welded gas turbine shroud and a process of forming an explosion-welded gas turbine

ABSTRACT

An explosion-welded turbine shroud and a process of forming an explosion-welded gas turbine shroud are disclosed. The explosion-welded gas turbine shroud includes a first alloy explosion welded to a second alloy. In the explosion-welded gas turbine shroud, the first alloy forms at least a portion of a hot gas path or an expansion region of the gas turbine shroud includes the first alloy. The process includes explosion welding a first alloy to a second alloy to form the gas turbine shroud.

FIELD OF THE INVENTION

The present invention is directed to manufactured components andprocesses of forming manufactured components. More specifically, thepresent invention relates to explosion-welded components and explosionwelding processes.

BACKGROUND OF THE INVENTION

The operating temperature within a gas turbine is both thermally andchemically hostile. Significant advances in high temperaturecapabilities have been achieved through the development of iron, nickel,and cobalt-based superalloys and the use of environmental coatingscapable of protecting superalloys from oxidation, hot corrosion, etc.,but coating systems continue to be developed to improve the performanceof the materials.

In the compressor portion of a gas turbine, atmospheric air iscompressed to 10-25 times atmospheric pressure, and adiabatically heatedto 800° F.-1250° F. (427° C.-677° C.) in the process. This heated andcompressed air is directed into a combustor, where it is mixed withfuel. The fuel is ignited, and the combustion process heats the gases tovery high temperatures, in excess of 3000° F. (1650° C.). These hotgases pass through the turbine, where airfoils fixed to rotating turbinedisks extract energy to drive an attached generator which produceselectrical power. To improve the efficiency of operation of the turbine,combustion temperatures have been raised. Of course, as the combustiontemperature is raised, steps must be taken to prevent thermaldegradation of the materials forming the flow path for these hot gasesof combustion.

Certain known alloys are used for components disposed along the flowpath of these hot gases. Certain portions of these components must beable to withstand temperatures higher than other portions of thesecomponents. For example, certain portions may be resistant totemperatures for adiabatic heating (for example, 800° F.-1250° F.) andother portions may be further resistant to hot gases heated by thecombustion processes (for example, in excess of 3000° F.). Componentsmade entirely of alloys resistant to the highest temperature may beundesirable by being overly expensive or failing to include otherproperties desirable in other portions of the components. Alternatively,components made entirely of alloys resistant only to the temperature ofthe lower temperature portions may fail.

Generally, gas turbine shrouds are manufactured from one or more ringsor cylinders. As such, manufacturing and tooling facilities areconfigured for manufacturing gas turbine shrouds from one or more ringsor cylinders. Welding of multiple materials to form gas turbine shroudsmay include techniques such as weld build-up, strip cladding, brazing,or solid state bonding. These techniques suffer from a drawback thatthey may be limited based upon properties of the materials (for example,crystal structures, compositions, or other suitable properties).

Explosion welding is a bonding technique that generally includes weldingplanar materials by an explosive force and results in a microstructurediffering from other weld techniques. Explosion welding permits metalsto be bonded that are otherwise generally incompatible. However,explosion welding processes have been limited to simple shapes andgeometries. Therefore, current explosion welding techniques have beenunable to bond structures in gas turbine shrouds.

An explosion-welded turbine shroud, an explosion-welded component, andan explosion-welding process that do not suffer from one or more of theabove drawbacks would be desirable in the art.

BRIEF DESCRIPTION OF THE INVENTION

According to an exemplary embodiment, a gas turbine shroud includes afirst alloy explosion welded to a second alloy. The first alloy forms atleast a portion of a hot gas path of the gas turbine shroud.

According to another exemplary embodiment, a gas turbine shroud includesan expansion region and a first alloy explosion welded to a secondalloy. The expansion region of the gas turbine shroud includes the firstalloy.

According to another exemplary embodiment, a process of forming anexplosion-welded gas turbine shroud includes explosion welding a firstalloy to a second alloy. The first alloy forms at least a portion of ahot gas path of the gas turbine shroud.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an exemplary explosion-welded gasturbine shroud according to an embodiment of the disclosure.

FIG. 2 shows an enlarged portion of an exemplary explosion-welded gasturbine shroud as shown in FIG. 1.

FIG. 3 shows a perspective view of an exemplary explosion-welded gasturbine shroud preform according to an embodiment of the disclosure.

FIG. 4 shows a perspective view of an exemplary explosion-welded gasturbine shroud preform according to an embodiment of the disclosure.

Wherever possible, the same reference numbers will be used throughoutthe drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

Provided is an explosion-welded gas turbine shroud, a non-planarexplosion-welded component, and a process of forming a non-planarexplosion-welded component. Embodiments of the present disclosure permitcomponents to be used in thermally and chemically hostile environments,permit components to be resistant to oxidation and/or hot corrosion,permit the overall material cost of components to be reduced incomparison to single alloy components, permit different portions ofcomponents to have different properties (for example, heat resistantproperties), permit non-planar components to have properties availablethrough explosion welding, permit materials having otherwiseincompatible properties to be bonded (for example, otherwiseincompatible crystal structures and/or compositions), and combinationsthereof.

FIG. 1 shows a non-planar explosion-welded component. Specifically, FIG.1 shows an explosion-welded gas turbine shroud 100. The shroud 100 isfor use in a gas turbine and is capable of being arrangedcircumferentially and concentric with a rotor (not shown) on whichturbine blades (not shown) are mounted. The shroud 100 includes ribs 107extending from a substantially planar member 109. In one embodiment, theribs 107 and the substantially planar member 109 include the samematerial. In another embodiment, the ribs 107 include material differentfrom the substantially planar member 109.

The shroud 100 includes a first alloy 102 and a second alloy 106. Thefirst alloy 102 is positioned along the substantially planar member 109as a cladding layer 104 and the second alloy 106 forms the substantiallyplanar member 109 and is a backing layer 108. The cladding layer 104 isresistant to heat above a first temperature (for example, about 1000°F., about 1250° F., about 1500° F., about 2000° F., or about 3000° F.).The backing layer 108 is resistant to heat above a second temperature(for example, between 800° F. and 1250° F., about 800° F., about 1000°F., about 1250° F., about 1500° F., or about 2000° F.). In oneembodiment, the first temperature is substantially higher than thesecond temperature. In a further embodiment, the second alloy 106 isunsuitable for being exposed to the first temperature.

The first alloy 102 is an austenitic alloy, such as austenitic stainlesssteel or austenitic manganese steel. The first alloy 102 is any suitablecladding material. Suitable cladding materials include, but are notlimited to, stainless steel alloys, aluminum alloys, tantalum alloys,nickel alloys, copper alloys, titanium alloys, zirconium alloys, andcombinations thereof In one embodiment, the second alloy 106 is anaustenitic alloy. In one embodiment, the second alloy 106 is a ferriticalloy such as ferritic stainless steel. The second alloy 106 is anysuitable backing material. Suitable backing materials include, but arenot limited to, carbon steel, chromium-molybdenum alloy steel, forgings,stainless steel, or combinations thereof.

Referring to FIG. 2, explosion welding of the first alloy 102 to thesecond alloy 106 forms a microstructure having a gradient 203 betweenthe first alloy 102 and the second alloy 106 as shown in enlarged region200 corresponding to FIG. 1. For example, in one embodiment with thefirst alloy 102 being austenitic and the second alloy 106 beingferritic, the first alloy 102 includes a large grain region 202 distalfrom the second alloy 106 and a fine grain region 204 proximal to thesecond alloy 106. In this embodiment, the second alloy 106 includes anamorphous region 206 proximal to the first alloy 102 and a highdislocation density region 208 distal from the first alloy 102. Theexplosion welding of the first alloy 102 to the second alloy 106 formsthe gradient 203 with a transition region 210 between the first alloy102 and the second alloy 106 thereby providing additional strength ofthe weld. As will be appreciated, in other embodiments, the first alloy102, the second alloy 106, and additional alloys (if present) areaustenitic or ferritic based upon desired properties.

Referring again to FIG. 1, the shroud 100 includes any other suitablefeatures such as cooling passages, notches, chambers, mounting features,or other suitable features. During operation, hot gas flows along a path101 abutting the cladding layer 104. The temperature of the gas within afirst region 103 abutting the path 101 is higher than the temperature ofthe gas within an expansion region 105 abutting the path 101. Theexpansion region 105 is identifiable by including an angled, arced, orotherwise expanded region formed along the path 101 of the gas.

FIGS. 3-4 show preforms 300 for forming the shroud 100. The preform 300is formed by explosion welding the first alloy 102 to the second alloy106. In the embodiment shown in FIG. 3, the preform 300 forms anembodiment of the shroud 100 with the first region 103 and the expansionregion 105 including the first alloy 102. In the embodiment shown inFIG. 4, the preform 300 forms an embodiment of the shroud 100 with theexpansion region 105 further including the second alloy 106.

In one embodiment of the process, the forming of the shroud 100 or anyother suitable component includes positioning a first portion of theshroud 100 and positioning a second portion of the shroud 100. The firstportion includes the first alloy 102 (for example, the cladding layer104) and the second portion includes the second alloy 106 (for example,the substantially planar member 109 or the backing layer 108). The firstportion and the second portion are explosion welded together to form thepreform 300. The preform 300 is then machined, deformed, further welded,or otherwise processed to remove excess material 302 and form thedesired features of the shroud 100. In an alternative embodiment wherethe preform 300 does not include the ribs 107, the ribs 107 are formedon the preform 300 after the explosion welding by removing materialthrough machining or by bonding the ribs 107 to the substantially planarmember 109.

The explosion welding of the first alloy 102 to the second alloy 106 isby ignition or initiation of detonation to direct the first alloy 102with explosive force to contact the second alloy 106. The explosionwelding is continued until a desired portion of the first alloy 102 isexplosion welded to the second alloy 106. The explosion welding isperformed along any suitable path. Suitable paths include, but are notlimited to, a helical path for a cylindrical component (or preform), aseries of paths, an S-shaped path, or combinations thereof. Inembodiments including a series of paths, multiple coordinated ignitionsor initiations of detonations coordinate the explosive welding (forexample, concurrent, sequential, or otherwise controlled detonations).

During the explosion welding process, the ignitions or detonations areperformed at predetermined conditions. In one embodiment, parametersinclude a predetermined pressure (for example, between about 1 GPa andabout 10 GPa, about 5 GPa, or about 10 GPa), a predetermined detonationrate (for example, between about 1500 m/s and 4000 m/s, between about1500 m/s and about 2000 m/s, between about 3500 m/s and about 4000 m/s,at about 1500 m/s, at about 2000 m/s, at about 3500 m/s, or at about4000 m/s), a predetermined impact angle (for example, between about 3°and about 30°, between about 3° and about 5°, between about 25° andabout 30°, at about 3°, at about 5°, at about 25°, or at about)30°, apredetermined collision velocity (for example, between about 225 m/s andabout 550 m/s, between about 225 m/s and about 250 m/s, between about500 m/s and about 550 m/s, at about 225 m/s, at about 250 m/s, at about500 m/s, or at about 550 m/s), or combinations thereof.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A gas turbine shroud, comprising: a first alloy explosion welded to asecond alloy; wherein the first alloy forms at least a portion of a hotgas path of the gas turbine shroud.
 2. The gas turbine shroud of claim1, wherein the first alloy is an austenitic alloy.
 3. The gas turbineshroud of claim 2, wherein the second alloy is an austenitic alloy. 4.The gas turbine shroud of claim 2, wherein the second alloy is aferritic alloy.
 5. The gas turbine shroud of claim 1, wherein the firstalloy is resistant to heat above a first temperature and the secondalloy is resistant to heat above a second temperature.
 6. The gasturbine shroud of claim 5, wherein the first temperature is greater thanthe second temperature.
 7. The gas turbine shroud of claim 5, whereinthe first temperature is above about 3000° F.
 8. The gas turbine shroudof claim 5, wherein the second temperature is between about 800° F. and1250° F.
 9. The gas turbine shroud of claim 1, further comprising anexpansion region positioned along the hot gas path.
 10. The gas turbineshroud of claim 9, wherein the expansion region includes the first alloyand the second alloy.
 11. The gas turbine shroud of claim 9, wherein theexpansion region consists of the first alloy.
 12. The gas turbine shroudof claim 1, wherein the first alloy decreases in thickness along the hotgas path.
 13. A gas turbine shroud, comprising: an expansion region; anda first alloy explosion welded to a second alloy; wherein the expansionregion of the gas turbine shroud includes the first alloy.
 14. The gasturbine shroud of claim 13, wherein the expansion region furtherincludes the second alloy.
 15. The gas turbine shroud of claim 13,wherein the expansion region consists of the first alloy.
 16. The gasturbine shroud of claim 13, wherein the expansion region is positionedalong a hot gas path and the first alloy decreases in thickness alongthe hot gas path.
 17. A process of forming an explosion-welded gasturbine shroud, comprising: explosion welding a first alloy to a secondalloy; wherein the first alloy forms at least a portion of a hot gaspath of the gas turbine shroud.
 18. The process of claim 17, wherein theexplosion welding of the first alloy to the second alloy forms apreform.
 19. The process of claim 18, further comprising removingmaterial from the preform.
 20. The process of claim 17, wherein theexplosion welding includes multiple concurrent detonations.